Systems and methods for collecting solar energy for conversion to electrical energy with piezoelectric generators

ABSTRACT

The present disclosure provides systems and methods for collecting and converting solar energy into electrical energy by using a solar collector and one or more piezoelectric generators. The present invention includes new designs for solar collectors that concentrate solar energy, and mechanisms for transporting and transferring the concentrated solar energy directly into the working fluid (e.g., a liquid, a gas, or a phase change substance) of the one or more piezoelectric generators without heating the outside surface of the engines. The system includes one or more solar collectors and a delivery system to deliver concentrated energy from the collectors directly into working fluid of one or more piezoelectric generators. Advantageously, the delivery system avoids heating an outside surface of the one or more piezoelectric generators as is done in conventional designs. Additionally, the delivery system can be configured to distribute collected energy to the one or more piezoelectric generators with offset heating cycles.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present non-provisional patent application is a continuation-in-partof co-pending U.S. patent application Ser. No. 12/212,249, filed Sep.17, 2008, and entitled “SYSTEMS AND METHODS FOR COLLECTING SOLAR ENERGYFOR CONVERSION TO ELECTRICAL ENERGY,” and co-pending U.S. patentapplication Ser. No. 12/212,408, filed Sep. 17, 2008, and entitled“APPARATUS FOR COLLECTING SOLAR ENERGY FOR CONVERSION TO ELECTRICALENERGY,” each of which claims priority to U.S. Provisional PatentApplication Ser. No. 60/993,946, filed Sep. 17, 2007, entitled “METHODAND APPARATUS FOR CONVERTING SOLAR ENERGY INTO ELECTRICAL ENERGY,” allof which are incorporated in full by reference herein. Additionally, thepresent non-provisional patent application claims priority to U.S.Provisional Patent Application Ser. No. 61/011,298, filed Jan. 16, 2008,entitled “METHOD AND APPARATUS FOR CONVERTING SOLAR ENERGY INTOELECTRICAL ENERGY USING CLOSED-CYCLE THERMODYNAMIC ENGINES ANDPIEZO-ELECTRIC GENERATORS,” to U.S. Provisional Patent Application Ser.No. 61/063,508, filed Feb. 4, 2008, entitled “METHOD AND APPARATUS FORCONVERTING SOLAR ENERGY INTO ELECTRICAL ENERGY USING MULTIPLECLOSED-CYCLE THERMODYNAMIC ENGINE AND PIEZO-ELECTRIC GENERATORS,” and toU.S. Provisional Patent Application Ser. No. 61/066,371, filed Feb. 20,2007, entitled “METHOD AND APPARATUS FOR CONVERTING ELECTROMAGNETICENERGY INTO ELECTRIC AND THERMAL ENERGY USING A CLOSED-CYCLETHERMODYNAMIC ENGINE AND ELECTRIC GENERATOR,” all of which areincorporated in full by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to solar energy conversion. Moreparticularly, the present invention provides systems and methods forcollecting and converting solar energy into electrical energy by using asolar collector and one or more piezoelectric generators.

BACKGROUND OF THE INVENTION

Solar energy is one of the renewable energy sources that does notpollute, it is free, and available virtually everywhere in the world.For these reasons, over the years there have been many systems andmethods that attempted to utilize solar energy and convert it into otherusable forms of energy such as electricity. More recently, due toperceived shortages and higher prices of fossil fuels and due topollution concerns, the interest has increased and the pace ofdevelopment of technologies that utilize alternative energy sources(such as solar) has accelerated.

There are two main techniques developed to harvest solar energy. Thefirst technique utilizes photovoltaic solar cells to directly convertsolar energy into electricity. The photovoltaic solar cells have theadvantage of small size, but are expensive to manufacture and the priceper watt has leveled due to the high cost of the semiconductor substrateutilized to construct the photovoltaic solar cells. There are many typesof designs and materials used to make photovoltaic solar cells whichaffect their cost and conversion efficiency. Current commerciallyavailable solar cells typically reach a starting efficiency around 18%which drops over time. The cells produce direct current (DC) that needsto be regulated, and for higher power applications typically the DCcurrent also needs to be converted to AC current.

The second technique utilizes the heat (infrared radiation) associatedwith the solar energy. Assuming that the goal is to generate electricalenergy, the solar radiation gets collected, concentrated, and utilizedas a heat source for various systems that convert the heat intomechanical energy, which is then converted into electrical energy.Successful machines developed to convert heat into mechanical energy canbe based on thermodynamic cycles. Mechanical energy produced by thesemachines is further converted into electrical energy by using rotatinggenerators or linear generators. For example, in the case of a Stirlingengine, heat (which can come from any heat source) is applied at one endof the engine and cooling is provided at a different location. Theworking fluid (gas), which is sealed inside the engine, goes through acycle of heating (expansion) and cooling (contraction). The cycle forcesa piston inside the engine to move and produce mechanical energy. Whenthe heat source is solar, successful engine designs use an intermediatemedium such as molten salt to more uniformly distribute the heat aroundthe outside surface of the heating end of the engine.

With respect to the second technique, problems arise when the surface ofthe engine is exposed to large temperature gradients due to closeproximity of the heat and cooling sources on the surface of the engine.For example, conventional engines can see extreme temperatures from dayto night and along the length of the engine body with temperaturesranging from over 1000 degrees Fahrenheit to room temperature across theengine body. Disadvantageously, these types of engines face difficultmaterial problems such as weld joint cracking and loss of materialproperties due to thermal cycling over time. Also, there are lossesassociated with heat radiation from the hot end of these types ofengines leading to inefficiency.

Piezoelectricity is the ability of some materials (notably crystals andcertain ceramics) to generate an electric potential in response toapplied mechanical stress. This can take the form of a separation ofelectric charge across the crystal lattice. If the material is notshort-circuited, the applied charge induces a voltage across thematerial. Direct piezoelectricity of some substances like quartz cangenerate potential differences of thousands of volts.

BRIEF SUMMARY OF THE INVENTION

In various exemplary embodiments, the present invention provides systemsand methods for collecting and converting solar energy into electricalenergy by using a solar collector and one or more piezoelectricgenerators. The present invention includes new designs for solarcollectors that concentrate solar energy, and mechanisms fortransporting and transferring the concentrated solar energy directlyinto the working fluid (e.g., a liquid, a gas, or a phase changesubstance) of the one or more piezoelectric generators without heatingthe outside surface of the engines. The system includes one or moresolar collectors and a delivery system to deliver concentrated energyfrom the collectors directly into working fluid of one or morepiezoelectric generators. Advantageously, the delivery system avoidsheating an outside surface of the one or more piezoelectric generatorsas is done in conventional designs. Additionally, the delivery systemcan be configured to distribute collected energy to the one or morepiezoelectric generators with offset heating cycles.

In an exemplary embodiment, a system for collecting solar energy for oneor more piezoelectric generators includes one or more piezoelectricgenerators each with a heat chamber; a solar collector configured toconcentrate solar energy; and a distribution mechanism configured todistribute the concentrated solar energy to the heat chambers in each ofthe one or more piezoelectric generators for a predetermined period oftime. The distribution mechanism is configured to distribute theconcentrated solar energy directly into the heat chambers in each of theone or more thermodynamic engines thereby reducing heating of an enginebody of each of the one or more piezoelectric generators. Each of theone or more piezoelectric generators can include any of: an opticallytransparent window shaped to reduce optical back reflection and to sealworking fluid in the heat chamber; and one or more light guidesextending into and terminating in the one or more chambers, wherein theone or more light guides each comprise an angled tip shaped to reduceoptical back reflection. Optionally, each of the one or morepiezoelectric generators include an optically transparent window shapedto reduce optical back reflection and to seal working fluid in the heatchamber; and the optically transparent window includes any of sapphireand fused silica. Alternatively, each of the one or more piezoelectricgenerators include one or more light guides extending into andterminating in the heat chambers; wherein the one or more light guideseach include an angled tip shaped to reduce optical back reflection; andwherein the one or more light guides are configured to combineconcentrated solar energy from a plurality of focusing/collimatingelements of the solar collection. The predetermined period of timeinclude a heating cycle for each of the one or more piezoelectricgenerators. The heating cycles for each of the one or more piezoelectricgenerators are offset from one another. Each of the one or morepiezoelectric generators include: piezoelectric element stacks disposedto the heat chamber through a flexible bellow section; and heat removingelements. Optionally, the distribution mechanism includes any of: anoptical switch configured to switch the concentrated solar energytowards each of the one or more piezoelectric generators; one or moreangled reflective surfaces; one or more light guides including amaterial that is substantially optically transparent; and rotatablereflective disks configured to either reflect or pass through theconcentrated solar energy responsive to relative position of each of therotatable reflective disks. Optionally, the heat removing elementsinclude tubes with circulating water.

In another exemplary embodiment, a method for collecting anddistributing solar energy to one or more piezoelectric generatorsincludes receiving collected and concentrated solar energy; anddirecting the concentrated solar energy into a heat chamber of each ofone or more piezoelectric generators for a predetermined time period.The method can further include configuring a solar collector to pointtowards the sun, wherein the solar collector is configured toconcentrate solar energy. Optionally, the method can further includeinflating a solar collector for concentrating solar energy. Thereceiving step can further include receiving solar energy through aplurality of focusing/collimating elements; and combining the receivedsolar energy through a plurality of light guides, optical switches, andoptical splitters/combiners. The directing step includes directlyproviding the concentrated solar energy into one of the heat chamberthrough one of: one or more optically transparent window shaped toreduce optical back reflection and to seal working fluid in the heatchamber; and one or more light guides extending into and terminating inthe heat chamber, wherein the one or more light guides each include anangled tip shaped to reduce optical back reflection. The predeterminedtime period includes heating cycles for each of the one or morepiezoelectric generators; and wherein the heating cycles for each of theone or more piezoelectric generators are offset from one another.

In yet another exemplary embodiment, a piezoelectric generator systemincludes a solar energy collection mechanism; a plurality of heatchambers each coupled to the solar energy collection mechanism; aplurality of piezoelectric element stacks each disposed to one of theheat chambers through a flexible bellow section; a switching element forthe solar energy collection mechanism, wherein the switching element isconfigured to distribute solar energy collected by the solar energycollection mechanism into the plurality of heat chambers in a pulsatingmanner. The piezoelectric generator system can further include heatremoving elements disposed to each of the plurality of heat chambers.Optionally, the heat removing elements include tubes with circulatingwater. Heating cycles for each of the plurality of heat chambers areoffset from one another.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated and described herein with referenceto the various drawings, in which like reference numbers denote likesystem components and/or method steps, respectively, and in which:

FIG. 1 is system schematic including a dual-surface reflector forcollecting and concentrating solar energy according to an exemplaryembodiment of the present invention;

FIG. 2 are multiple low-profile solar collectors for providing a flatterand compact low-profile arrangement according to an exemplary embodimentof the present invention;

FIG. 3 is a mechanism for combining solar radiation from multiplelow-profile solar collectors through light guides according to anexemplary embodiment of the present invention;

FIG. 4 is a diagram of various designs for a focusing/collimatingelement according to an exemplary embodiment of the present invention;

FIGS. 5A and 5B are partial cross-sectional views of a piezoelectricgenerator according to an exemplary embodiment of the present invention;

FIG. 6 is a diagram of an energy distribution and delivery system forconcentrated solar energy directly into piezoelectric generatorsaccording to an exemplary embodiment of the present invention;

FIG. 7 is a flowchart of an energy distribution and delivery mechanismfor concentrating and releasing solar energy in a pulsating mannerdirectly into piezoelectric generators according to an exemplaryembodiment of the present invention; and

FIG. 8 is a flow chart of a mechanism to convert solar energy intoelectric energy according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

In various exemplary embodiments, the present invention provides systemsand methods for collecting and converting solar energy into electricalenergy. The present invention includes solar collectors that concentratesolar energy and mechanisms for transporting and transferring theconcentrated solar energy directly into one or more piezoelectricgenerators without heating the outside surface of the engines.Additionally, the present invention includes mechanisms to direct solarenergy into each of the one or more piezoelectric generators to increaseoverall system efficiency by maximizing the use of collected solarenergy. Advantageously, the delivery system of the present inventionavoids heating an outside surface of the one or more piezoelectricgenerators as is done in conventional designs, provides a closed designto protect the collectors, and maximizes efficiency through multiplegenerators and optical splitters.

Referring to FIG. 1, a dual-surface reflector 100 is illustrated forcollecting and concentrating solar energy 102 according to an exemplaryembodiment of the present invention. The dual-surfaces on thedual-surface reflector 100 include a primary reflector 104 and asecondary reflector 106. The reflectors 104, 106 can be in a parabolicshape, a spherical shape, and the like. Also, the secondary reflector106 can be concave or convex depending on the positioning of thesecondary reflector 106 relative to the primary reflector 104. Theprimary reflector 104 is pointed towards the solar energy 102, and thesecondary reflector 106 is located above the primary reflector 104. Theprimary reflector 104 is configured to reflect the solar energy 102 tothe secondary reflector 106 which in turn concentrates the solar energy102 through an opening 108 at a center of the primary reflector 104.

An outer perimeter support ring 110 is disposed around the edges of theprimary reflector 104 to maintain the shape of the primary reflector 104and to anchor in place the primary reflector 104. A transparent andflexible material 112 connects to the primary reflector 104 and to thesupport ring 110 to hold the secondary reflector 106 in place. Thetransparent and flexible material 112 is configured to allow the solarenergy 102 to pass through, and can be constructed from a material thatis optically transparent in the infrared region, such as a material inthe Teflon® family of products, for example, fluorinated ethylenepropylene (FEP) or the like. The transparent and flexible material 112provides a closed design of the dual-surface reflector 100.Advantageously, the transparent and flexible material 112 can seal thedual-surface reflector 100 from the elements, i.e. wind, airborneparticles, dirt, bird droppings, etc. This prevents deterioration of thereflectors 104, 106 and reduces maintenance with respect to cleaning thereflectors 104, 106.

A support member 114 can be disposed to the outer perimeter support ring110 and a base 116. The base 116 can connect to a tracking mechanism 118through a rotatable member 120. The tracking mechanism 118 is configuredto continuously point the reflectors 104, 106 towards the sun byinitiating a rotation of the rotatable member 120 to rotate the base116, the support member 114 and the support ring 110. For example, thetracking mechanism 118 can include a microcontroller or the like canrotate according to location (e.g., an integrated Global PositioningSatellite (GPS) receiver, preprogrammed location, or the like), date,and time or the like. Additionally, the tracking mechanism 118 caninclude feedback from sensors that detect the position of the sun.

The base 116 can include one or more motors and electric generators 122,124. The opening 108 is connected to the base 116 to provideconcentrated solar energy from the reflectors 104, 106 to the one ormore motors and electric generators 122, 124. For a single motor andelectric generator 122, the motor and electric generator 122 ispositioned to allow the concentrated solar energy to enter working fluid(e.g., a liquid, a gas, or a phase change substance) without heating anoutside surface of the single motor and electric generator 122. The oneor more motors and electric generators 122, 124 can includepiezoelectric generators or variations of these.

FIG. 1 illustrates an exemplary embodiment with two of the motors andelectric generators 122, 124. This exemplary embodiment includes anoptical switch 126 and reflecting surfaces 128 to direct theconcentrated solar energy into each of the motors and electricgenerators 122, 124. Those of ordinary skill in the art will recognizethat the base 116 can include more than two of the motors and electricgenerators 122, 124 with a corresponding optical switch 126 andreflecting surfaces 128 to concentrate solar energy into each of themore than two of the motors and electric generators 122, 124. Theoptical switch 126 is configured to provide concentrated solar energyfor predetermined intervals into each of the motors and electricgenerators 122, 124.

Advantageously, the optical switch 126 enables the dual-surfacereflector 100 to input energy into each of the motors and electricgenerators 122, 124 in a pulsating manner only when needed and for aduration of time that is completely controllable. This enables thedual-surface reflector 100 to avoid wasting collected solar energy, i.e.the optical switch 126 enables the collected energy to be used in eachof the motors and electric generators 122, 124 as needed. For example,the optical switch 126 can be configured to direct collected solarenergy into a heating chamber of each of the motors and electricgenerators 122, 124 only during a heating cycle. The motors and electricgenerators 122, 124 each have offset heating cycles to allow allcollected solar energy to be used, i.e. the optical switch 126 cyclesbetween each of the motors and electric generators 122, 124 for theirindividual heating cycles.

In an exemplary embodiment, the dual-surface reflector 100 can includeinflatable components, such as an inflatable portion 130 between theprimary reflector 104 and the secondary reflector 106 and in the outerperimeter support ring 110. Air lines 132, 134 can be connected to theinflatable portion 130 and the outer perimeter support ring 110,respectively, to allow inflation through a valve 136, a pressure monitor138, and an air pump 140. Additionally, a microcontroller 142 can beoperably connected to the air pump 140, the pressure monitor 138, thevalve 136, the tracking mechanism 118, etc. The microcontroller 142 canprovide various control and monitoring functions of the dual-surfacereflector 100.

Collectively, the components 136, 138, 140, 142 can be located withinthe base 116, attached to the base 116, in the tracking mechanism 118,external to the base 116 and the tracking mechanism 118, etc. The valve136 can include multiple valves, such as, for example, an OFF valve, anON/OFF line 132/134 valve, an OFF/ON ON/OFF line 132/134 valve, and soon for additional lines as needed, or the valve 136 can include multipleindividual ON/OFF valves controlled by the microcontroller 142.

The inflatable components can be deflated and stored, such as in acompartment of the base 114. For example, the inflatable componentscould be stored in inclement weather, high winds, and the like toprotect the inflatable components from damage. The microcontroller 142can be connected to sensors which provide various feedback regardingcurrent conditions, such as wind speed and the like. The microcontroller142 can be configured to automatically deflate the inflatable componentsresponsive to high winds, for example.

The support member 114 and the outer perimeter support ring 110,collectively, are configured to maintain the desired shape of theprimary reflector 104, the secondary reflector 106, and the transparentand flexible material 112. The pressure monitor 138 is configured toprovide feedback to the microcontroller 142 about the air pressure inthe inflatable portion 130 and the outer perimeter support ring 110. Thedual-surface reflector 100 can also include controllable relief pressurevalves (not shown) to enable the release of air to deflate thedual-surface reflector 100. The transparent and flexible material 112can form a closed space 130 which is inflated through the air line 132to provide a shape of the secondary reflector 106, i.e. air is includedin the interior of the dual-surface reflector 100 formed by thetransparent and flexible material 112, the secondary reflector 106 andthe primary reflector 104.

Advantageously, the inflatable components provide low cost and lowweight. For example, the inflatable components can reduce the loadrequirements to support the dual-surface reflector 100, such as on aroof, for example. Also, the inflatable components can be transportedmore efficiently (due to the low cost and ability to deflate) and storedwhen not in use (in inclement weather, for example).

In another exemplary embodiment, the primary reflector 104, the supportmember 114, the outer perimeter support ring 110, the transparent andflexible material 112, etc. could be constructed through rigid materialswhich maintain shape. In this configuration, the components 136, 138,140 are not required. The microcontroller 142 could be used in thisconfiguration for control of the tracking mechanism 118 and generaloperations of the dual-surface reflector 100.

In both exemplary embodiments of the dual-surface reflector 100, themicrocontroller 142 can include an external interface, such as through anetwork connection or direct connection, to enable user control of thedual-surface reflector 100. For example, the microcontroller 142 caninclude a user interface (UI) to enable custom settings.

The primary reflector 104 can be made from a flexible material such as apolymer (FEP) that is metalized with a thin, highly reflective metallayer that can be followed by additional coatings that protect andcreate high reflectance in the infrared region. Some of the metals thatcan be used for depositing a thin reflector layer on the polymersubstrate material of the inflatable collector can include gold,aluminum, silver, or dielectric materials. Preferably, the surface ofthe primary reflector 104 is metalized and coated such that it isprotected from contamination, scratching, weather, or other potentiallydamaging elements.

The secondary reflector 106 surface can be made in the same manner asthe primary reflector 104 with the reflecting metal layer beingdeposited onto the inside surface of the secondary reflector 106. Forimproved performance, the secondary reflector 106 can be made out of arigid material with a high precision reflective surface shape. In thiscase the, the secondary reflector can be directly attached to thetransparent and flexible material 112 or be sealed to it (impermeable toair) around the perimeter of the secondary reflector 106. Both theprimary reflector 104 and the secondary reflector 106 can utilizetechniques to increase surface reflectivity (such as multi-layers) toalmost 100%.

The dual-surface reflector 100 operates by receiving the solar energy102 through solar radiation through the transparent and flexiblematerial 112, the solar radiation reflects from the primary reflector104 onto the secondary reflector 106 which collimates or slightlyfocuses the solar radiation towards the opening 108. One or more engines(described in FIG. 5) can be located at the opening 108 to receive theconcentrated solar radiation (i.e., using the optical switch 126 and thereflectors 128 to enable multiple engines). The collimated or focusedsolar radiation from the secondary reflector 106 enters throughoptically transparent window on the engines towards a hot end (solarenergy absorber) of a thermodynamic engine.

Advantageously, the dual-surface reflector 100 focuses the solar energy102 and directs it into each of the motors and electric generators 122,124 for their individual heating cycles in a manner that avoids heatingengine components other than the solar energy absorber element in theheating chamber of the motors and electric generators 122, 124.Specifically, the opening 108 extends to the optical switch 126 whichdirects the concentrated solar energy directly into each of the motorsand electric generators 122, 124 through a transparent window of theheating chamber. The materials forming the opening 108 and thetransparent window include materials with absorption substantially closeto zero for infrared radiation.

The dual-surface reflector 100 includes a large volume, and ispreferably suitable for open spaces. For example, the dual-surfacereflector 100 could be utilized in open-space solar farms for powerplants, farms, etc. In an exemplary embodiment, the dual-surfacereflector 100 could be four to six meters in diameter. Alternatively,the dual-surface reflector 100 could be a reduced size for individualhome-use. Advantageously, the light weight of the inflatable componentscould enable use of the dual-surface reflector 100 on a roof. Forexample, a home-based dual-surface reflector 100 could be 0.1 to onemeters in diameter. Also, the reduced cost could enable the use of thedual-surface reflector 100 as a backup generator, for example.

Referring to FIG. 2, multiple solar collectors 200 are illustrated forproviding a flatter and compact arrangement, i.e. a low-profile design,according to an exemplary embodiment of the present invention. FIG. 2illustrates a top view and a side view of the multiple solar collectors200. In the top view, the multiple solar collectors 200 can be arrangedside-by-side along an x- and y-axis. Each of the solar collectors 200includes a focusing/collimating element 202 which is configured toconcentrate solar radiation 102 into a corresponding light guide 204.The focusing/collimating element 202 is illustrated in FIG. 2 with anexemplary profile, and additional exemplary profile shapes areillustrated in FIG. 4.

The focusing/collimating element 202 focuses the solar radiation 102into a cone of light with a numerical aperture smaller than thenumerical aperture of the light guide 204. The focusing/collimatingelement 202 can be made out of a material transparent to infrared solarradiation, such as FEP. The focusing/collimating element 202 can be asolid material or hollow with a flexible skin that allows the element202 to be formed by inflating it with a gas. Forming the element thoughinflation provides weight and material costs advantages.

The light guides 204 can be constructed out of a material that isoptically transparent in the infrared region, such as FEP, glass, orother fluorinated polymers in the Teflon® family, or the light guides204 can be made out of a thin tube (e.g., FEP) filled with a fluid, suchas Germanium tetrachloride or Carbon tetrachloride, that is transparentto infrared radiation. Advantageously, the light guides 204 include amaterial selected so that it has close to zero absorption in thewavelengths of the solar energy 102. The tube material must have ahigher index of refraction than the fluid inside it in order to create astep index light guide that allows propagation of the concentrated solarradiation. The array of the multiple solar collectors 200 can extend inthe X and Y direction as needed to collect more solar energy.

The focusing/collimating element 202, the light guide 204 and theinterface 206 can be rotatably attached to a solar tracking mechanism(not shown). The tracking mechanism is configured to ensure thefocusing/collimating element 202 continuously points toward the sun. Amicrocontroller (not shown) similar to the microcontroller 142 in FIG. 1can control the tracking mechanism along with other functions of themultiple solar collectors 200. The tracking mechanism can individuallypoint each of the focusing/collimating elements 202 towards the Sun, oralternatively, a group tracking mechanism (not shown) can align a groupof elements 202 together.

Referring to FIG. 3, a mechanism 300 is illustrated for combining solarradiation 102 from the multiple light guides 204 in FIG. 2 according toan exemplary embodiment of the present invention. The multiple lightguides 204 are configured to receive concentrated solar radiation fromthe focusing/collimating elements 202 and to guide it and release itinside a hot end of one or more piezoelectric generators. Opticalcouplers 302 can be utilized to combine multiple light guides 204 into asingle output 304. For example, FIG. 3 illustrates four total lightguides 204 combined into a single output 306 through a total of threecascaded optical couplers 302. Those of ordinary skill in the art willrecognize that various configurations of optical couplers 302 can beutilized to combine an arbitrary number of light guides 204. The opticalcouplers 204 which are deployed in a tree configuration in FIG. 3 reducethe number of light 204 guides reaching the one or more piezoelectricgenerators. Alternatively, each light guide 204 could be directedseparately into the one or more piezoelectric generators.

An optical splitter 308 and an optical switch 310 can also be includedin the optical path (illustrated connected to a light guide 312 whichincludes a combination of all of the light guides 204) at an optimumlocation along each light guide 204 leading to one or more piezoelectricgenerators. The optical splitter 308 and optical switch 310 permitpulsation of the concentrated solar energy into one or morepiezoelectric generators. Each branch (e.g., two or more branches) ofthe optical splitter 308 leads to a different piezoelectric generator.The optical switch 310 sequentially directs the concentrated solarenergy traveling along the light guide 312 into different arms of theoptical splitter 308. For example, the one or more piezoelectricgenerators can include offset heating cycles with the optical splitter308 and the optical switch 310 directing solar energy 102 into eachengine at its corresponding heating cycle. Advantageously, this improvesefficiency ensuring that collected solar energy 102 is not wasted (aswould occur if there was a single engine because the single engine onlyrequires the energy during the heating cycle).

The optical switch 310 can be integrated into the optical splitter 308as indicated in FIG. 3 or it can exist independently in which case theoptical splitter 308 could be eliminated and the optical switch 310 canhave the configuration presented in FIG. 1 (i.e., optical switch 126 andreflecting surfaces 128). In the case where the optical switch 310 isindependent of the light guide 312, the light guide termination isdesigned to collimate the light directed towards the optical switch 310.The selection of the optimum points where the optical splitters 308 areinserted depends on the power handling ability of the optical switch 310and on economic factors. For example, if the optical switch 310 isinserted in the optical path closer to the one or more piezoelectricgenerators, then fewer switches 310 and shorter light guides 204 areneeded, but the optical switches 310 need to be able to handle higherlight intensities.

Referring to FIG. 4, various designs are illustrated for thefocusing/collimating element 202 a-202 e according to an exemplaryembodiment of the present invention. The focusing/collimating element202 a, 202 b, 202 c each include an optically transparent solid material402 shaped in either a bi-convex (element 202 a), a plano-convex(element 202 b), and a meniscus form (element 202 c), all of which havethe purpose to focus the incoming solar energy 102. Additionally, eachof the elements 202 a, 202 b, 202 c also include a flexible “skin”material 404 that together with the optically transparent solid material402 form an inflatable structure 406 which can be inflated with air or adifferent gas. The air/gas pressure in the inflatable structure 406 canbe dynamically controlled to maintain an optimum focal distance betweenthe solid material 402 and the one or more piezoelectric generators. Theoptically transparent solid material 402 and the flexible “skin”material 404 are made out of a material transparent to visible andinfrared solar radiation, such as FEP, for example. Thefocusing/collimating element 202 d is a solid convex focusing elementconstructed entirely of the optically transparent solid material 402.

The focusing/collimating element 202 e includes an inflatable dualreflector including a primary reflecting surface 408 and a smallersecondary reflecting surface 410 inside an inflatable structure 406. Theprimary reflecting surface 408 and the secondary reflecting surface 410are configured to collectively concentrate the solar radiation 102 intoan opening 412 that leads to the light guide 204. Both reflectingsurfaces 408, 410 can be rigid or flexible such as metalized films oronly the secondary reflector 410 can be made out of a rigid materialwith a high precision reflective surface shape. In this case, thesecondary reflector 410 can be directly attached to the transparentmaterial 404 or can be sealed to it (impermeable to air) around theperimeter of the secondary reflector 410. Some of the metals that can beused for metalizing a thin reflector layer on the polymer substratematerial of the inflatable collector can include gold, aluminum, silver,or dielectric materials. The preferred surface to be metalized is theinside of the inflatable solar collector such that it is protected fromcontamination, scratching, weather, or other potentially damagingelements.

Techniques to increase surface reflectivity (such as multi layerdielectric coatings) to almost 100% can be utilized. Again, the air/gaspressure can be dynamically controlled, based on feedback from pressuresensors monitoring the inside pressure of the inflatable focusingelement, to maintain the optimum focal distance. All transparentmaterials through which solar radiation and concentrated solar radiationpasses through can have their surfaces covered with broad bandanti-reflective coatings in order to maximize light transmission. Thedesigns of the focusing elements 202 presented in FIG. 3 are forillustration purposes and those of ordinary skill in the art willrecognize other designs are possible that would meet the purpose andfunctionality of the focusing elements 202.

The multiple solar collectors 200 can be utilized in buildings, such asoffice buildings, homes, etc. For example, multiple focusing/collimatingelements 202 can be placed on a roof with the light guides 204 extendinginto the building towards a service area, basement, etc. to one or morethermodynamic engines or generators. Additionally, the light guides 204heat up very little based upon their material construction.Advantageously, the low profile design of the solar collectors 200enables roof placement and the light guides enable a separate enginelocation within a building.

Referring to FIGS. 5A and 5B, a partial cross-sectional view illustratesa piezoelectric generator 500 according to an exemplary embodiment ofthe present invention. FIG. 5A illustrates an exemplary embodiment whereconcentrated solar energy 102 travels through free space to enter thegenerator 500 through an optically transparent window 502. Also,multiple optically transparent windows 502 could be utilized. Theoptically transparent window 502 is made out of a material transparentto infrared radiation, such as sapphire, fused silica or the like. Theshape of the optically transparent window 502 is such that itfacilitates sealing of working fluid inside the generator 500 andreduction of back reflection. FIG. 5A shows a trapezoidal cross sectionof the optically transparent window 502 as an exemplary embodiment. Theoptically transparent window 502 can be disposed at an end of theopening 108 or placed adjacent to the reflecting surfaces 128 of thedual-surface reflector 100 in FIG. 1.

FIG. 5B illustrates an exemplary embodiment where concentrated solarradiation enters the generator 500 through a plurality of light guides504. Each of the light guides 504 includes a termination 506 that ismade out of material transparent to infrared radiation and that is alsoresistant to the high temperatures inside the generator 500. The shapeof termination 506 facilitates sealing of working fluid inside thegenerator 506. FIG. 5B shows a trapezoidal cross section of thetermination 506. The termination 506 has an angled tip inside thegenerator 500 that minimizes back reflection inside the light guide 504and also minimizes coupling back into the light guide 506 of radiationfrom the generator 500. The termination 506 includes a very hardmaterial with good optical properties able to withstand hightemperatures. The plurality of light guides 504 can connect to the solarcollectors 200 in FIGS. 2-4. Additionally, the generator 500 can includefewer light guides 504 than solar collectors 200 utilizing the mechanism300 in FIG. 3 to combine light guides 204.

In both FIGS. 5A and 5B, the optically transparent window 502 and theplurality of light guides 504 transfer concentrated solar energydirectly into a heat chamber 508 of the generator 500. Advantageously,this direct transfer provides a lower temperature of the generator 500and reduced thermal stress on a generator body 510 of the generator 500.This leads to longer generator 500 life, better reliability, increasedefficiency, and the like.

Additionally, the optically transparent window 502 and the plurality oflight guides 504 can be configured to transfer the solar energy in apulsating manner. The pulsating manner means that the solar energy isallowed to enter into the chamber 508 of the generator 500 periodically,for a predetermined period of time, similar to turning a switch ON andOFF. During the OFF period for a particular generator 500, the solarenergy is directed into a second, or third, or other generator 500 in arotating, periodical fashion. In this way, all the energy from thecollector is utilized. Also, during the OFF period for a particulargenerator 500, heat is removed from working fluid 510 as part of thethermodynamic cycle. An advantage of pulsating the energy is that solarenergy is added to the working fluid 510 in a controlled manner only atthe desired time.

Transferring the concentrated solar energy directly into the heatchamber 508 of the generator 500 provides great benefits. The generatorbody 510 has a lower temperature and the thermal stress and thermalaging in the body 510 is reduced. The chamber 508 can be surrounded byheat removing elements 512 such as any type of heat exchanger. The heatexchanger can actually be located inside the chamber 508 to maximize therate of heat transfer and prevent the walls of the generator 500 fromheating up excessively. In an exemplary embodiment, the heat removingelements 512 can include tubes with circulating water being used toremove heat. The heat extracted into the cooling water can be dissipatedinto the air through another heat exchanger or can be used as a heatsource for heating, for example, household water.

Advantageously, inserting the solar energy directly into the workingfluid 510 in a pulsating manner can improve the efficiency of thegenerator 500 because the outside temperature of the hot end of thegenerator 500 can be greatly reduced and therefore the radiated heatloss is decreased. The working fluid 510 can be a gas, typicallypressurized, steam, a phase change material, or any other working fluidutilized in closed-cycle thermodynamic engines. The working fluid 510can include an energy absorbing material that is designed to have alarge surface area and is made out of a material that absorbs infraredradiation and that can efficiently release it to the working fluid. Suchmaterials include graphite or other type of carbon based material, asuitable metal, or a metal oxide. The energy absorber can be alsoinclude carbon nano particles or other nano size particles uniformlydistributed and suspended in the working fluid 510.

A bottom portion 514 of the generator 500 and the heat chamber 510 areattached in a sealed manner through a flexible bellow section 516 thatallows the bottom portion 514 to move when the pressure in the heatchamber 510 increases. As a result, the stacks of piezoelectric elements518 are compressed and a voltage is generated. The piezoelectricelements 518 can be connected in series or parallel (or combination ofseries and parallel) to generate the desired voltage and current. Theelectrical energy can be distributed for use or stored for future use.

The generator 500 is shown for illustration purposes. Those of ordinaryskill in the art will recognize that the dual-surface reflector 100 andthe multiple solar collectors 200 can be utilized to concentrate anddirectly deliver solar energy into any type of generator.

Advantageously, the designs described herein enable distributedelectrical energy generation from a few kWs to 10's of kW per unit at alow cost. The present invention can directly generate AlternatingCurrent (AC) electricity without a need for inverters. Also, the presentinvention can provide heat output which can be used, for example, forspace heating, water heating, air conditioning, micro desalinationplants, and the like. The present invention provides low installationcosts and low overall maintenance costs. Additionally, the presentinvention can enable a modular design, such as adding additional solarcollectors as needed to scale energy generation.

Referring to FIG. 6, an energy distribution and delivery system 600 isillustrated for concentrated solar energy that allows the release of theconcentrated solar energy in a pulsating manner directly into one ormore piezoelectric generators according to an exemplary embodiment ofthe present invention. The energy distribution and delivery system 600is illustrated with two exemplary piezoelectric generators 602 a, 602 b,and those of ordinary skill in the art will recognize the energydistribution and delivery system 600 could use additional piezoelectricgenerators 602.

Each of the piezoelectric generators 602 a, 602 b includes a firstheating chamber 604 a, 604 b and a second heating chamber 606 a, 606 b.The energy distribution and delivery system 600 is configured tomaximize usage of collected solar energy 102 by distributing the solarenergy 102 to each heating chamber 604 a, 604 b, 606 a, 606 b atappropriate times in their respective cycles. For example, the solarenergy 102 can be collected utilizing the dual-surface reflector 100and/or the multiple solar collectors 200 described herein.

The energy distribution and delivery system 600 includes multiplereflective disks 610, 612, 614, 616 for distributing the collected solarenergy 102. Note, these reflective disks 610, 612, 614, 616 could beincluded within a light guide, for example. Additionally, the opticalswitch and splitter described herein could provide similar functionalityto the reflective disks 610, 612, 614, 616. The reflective disks 610,612, 614, 616 are configured to either reflect or pass through thecollected solar energy 102. Additionally, each of the reflective disks610, 612, 614, 616 is configured to rotate to either reflect or passthrough the collected solar energy 102.

FIG. 6 illustrates an exemplary operation of the energy distribution anddelivery system 600. The collected solar energy 102, during a timeperiod 620 (following a dashed line A), passes through an opening of thefirst disk 610 and enters the heating chamber 604 a of the generator 602a. During a time period 622 (following a dashed line B), theconcentrated solar energy 102 is reflected off the first disk 610,passes through the second disk 612, and reflects off the third disk 616to enter the heating chamber 604 b of the generator 602 b.

During a time period 624 (following a dashed line C), the concentratedsolar energy 102 reflects off the first disk 610, reflects off thesecond disk 612, and reflects off reflectors 630, 632 to enter theheating chamber 606 a of the generator 602 a. The reflectors 630, 632are positioned to direct the concentrated solar energy 102, and lightguides could also be utilized. During a time period 634 (following adashed line D), the concentrated solar energy 102 reflects off the firstdisk 610, passes through the second disk 612 and the third disk 614, andreflects off the fourth disk 616 and reflective surfaces 640, 642 toenter the heating chamber 606 b of the generator 602 b.

The cycle can then start all over again. The energy distribution anddelivery system 600 can be used for one, two, or more generator chainedin a similar fashion. The size and shape of the reflecting surfaces oneach individual disk can be tailored for obtaining optimum performance.For example, the duration of the energy input in any chamber 604 a, 604b, 606 a, 606 b can be adjusted by varying the size of the reflectingsurface (or a combination of multiple reflecting surfaces) and therotational speed of the disk 610, 612, 614, 616. The energy distributionand delivery system 600 can include motors (not shown) configured torotate the disks 610, 612, 614, 616. The pulsating manner of energytransfer allows the solar energy to enter into the chamber of thegenerator periodically, for a controllable period of time, similar toturning a switch ON and OFF. Also, the energy distribution and deliverysystem 600 can utilize the optical splitter 308 and the optical switch310 in a similar fashion as the reflective disks 610, 612, 614, 616 todistribute the solar energy 102.

Referring to FIG. 7, a flowchart illustrates an energy distribution anddelivery mechanism 700 for concentrating and releasing solar energy in apulsating manner directly into thermodynamic closed-cycle basedgenerators according to an exemplary embodiment of the presentinvention. The distribution and delivery mechanism 700 collects solarenergy (step 702). The collection step can include the mechanismsdescribed herein with respect to the dual-surface reflector 100 and/orthe multiple solar collectors 200.

Next, the distribution and delivery mechanism 700 directs the collectedsolar energy to a first heat chamber in a first generator for apredetermined time period (step 704). The predetermined time period cancorrespond to a heating cycle for the first generator. After thepredetermined time period, the collected solar energy is directed to anext first heat chamber in a next generator for another predeterminedtime period (step 706).

The distribution and delivery mechanism 700 checks if there is anothergenerator (step 708). Here, the distribution and delivery mechanism 700is configured to cycle through all of the generators to providecollected solar energy into the associated first heat chambers of eachgenerator. If there is another generator, the distribution and deliverymechanism 700 returns to step 706.

If not, the distribution and delivery mechanism 700 directs thecollected solar energy to a second heat chamber in the first generatorfor a predetermined time period (step 710). Then, the distribution anddelivery mechanism 700 directs the collected solar energy to a nextsecond heat chamber in the next generator for a predetermined timeperiod (step 712).

The distribution and delivery mechanism 700 checks if there is anotherthermodynamic engine (step 714). Here, the distribution and deliverymechanism 700 is configured to cycle through all of the generators toprovide collected solar energy into the associated second heat chambersof each generator. If there is another generator, the distribution anddelivery mechanism 600 returns to step 716. If not, the distribution anddelivery mechanism 600 can return to step 704 for another cycle througheach of the heat chambers.

Referring to FIG. 8, a flow chart illustrates a mechanism 800 to convertsolar energy into electric energy according to an exemplary embodimentof the present invention. The mechanism 800 includes: continuouslypositioning one or more solar collectors towards the sun (step 802);collecting solar radiation at each of the one or more solar collectors(step 804); directing the collected solar radiation to a heat chamber ina generator (step 806); periodically and controllably heating a workingfluid in the generator with the directed solar radiation (step 808);reciprocating a piezoelectric generator responsive to pressure changesin the working fluid (step 810); collecting the generated electricalenergy (step 812); cooling the working fluid (step 814), and repeatingthe mechanism 800.

Although the present invention has been illustrated and described hereinwith reference to preferred embodiments and specific examples thereof,it will be readily apparent to those of ordinary skill in the art thatother embodiments and examples may perform similar functions and/orachieve like results. All such equivalent embodiments and examples arewithin the spirit and scope of the present invention and are intended tobe covered by the following claims.

1. A system for collecting solar energy for one or more piezoelectricgenerators, the system comprising: one or more piezoelectric generatorseach comprising a heat chamber; a solar collector configured toconcentrate solar energy; and a distribution mechanism configured todistribute the concentrated solar energy to the heat chambers in each ofthe one or more piezoelectric generators for a predetermined period oftime, wherein the distribution mechanism directly connects the solarcollector to the heat chamber in each of the one or more piezoelectricgenerators.
 2. The system of claim 1, wherein the distribution mechanismis configured to distribute the concentrated solar energy directly fromthe solar collector into the heat chambers in each of the one or morethermodynamic engines thereby reducing heating of an engine body of eachof the one or more piezoelectric generators, and wherein theconcentrated solar energy is converted to heat within the heat chambersand not outside the heat chambers.
 3. The system of claim 2, whereineach of the one or more piezoelectric generators comprise any of: anoptically transparent window shaped to reduce optical back reflectionand to seal working fluid in the heat chamber; and one or more lightguides extending into and terminating in the one or more chambers,wherein the one or more light guides each comprise an angled tip shapedto reduce optical back reflection.
 4. The system of claim 2, whereineach of the one or more piezoelectric generators comprise an opticallytransparent window shaped to reduce optical back reflection and to sealworking fluid in the heat chamber; and wherein the optically transparentwindow comprises any of sapphire and fused silica.
 5. The system ofclaim 2, wherein each of the one or more piezoelectric generatorscomprise one or more light guides extending into and terminating in theheat chambers; wherein the one or more light guides each comprise anangled tip shaped to reduce optical back reflection; and wherein the oneor more light guides are configured to combine concentrated solar energyfrom a plurality of focusing/collimating elements of the solarcollection.
 6. The system of claim 1, wherein the predetermined periodof time comprises a heating cycle for each of the one or morepiezoelectric generators.
 7. The system of claim 6, wherein the heatingcycles for each of the one or more piezoelectric generators are offsetfrom one another.
 8. The system of claim 7, wherein each of the one ormore piezoelectric generators comprise: piezoelectric element stacksdisposed to the heat chamber through a flexible bellow section; and heatremoving elements.
 9. The system of claim 1, wherein the distributionmechanism comprises any of: an optical switch configured to switch theconcentrated solar energy towards each of the one or more piezoelectricgenerators; one or more angled reflective surfaces; one or more lightguides comprising a material that is substantially opticallytransparent; and rotatable reflective disks configured to either reflector pass through the concentrated solar energy responsive to relativeposition of each of the rotatable reflective disks.
 10. The system ofclaim 7, wherein the heat removing elements comprise tubes withcirculating water.
 11. A method for collecting and distributing solarenergy to one or more piezoelectric generators, the method comprising:receiving collected and concentrated solar energy from a solarcollector; and directing the concentrated solar energy from the solarcollector into a heat chamber of each of one or more piezoelectricgenerators for a predetermined time period, wherein the concentratedsolar energy is converted to heat within the heat chambers and notoutside the heat chambers.
 12. The method of claim 11, the methodfurther comprising: configuring the solar collector to point towards thesun, wherein the solar collector is configured to concentrate solarenergy.
 13. The method of claim 11, the method further comprising:inflating the solar collector for concentrating solar energy, whereinthe solar collector comprises inflatable components.
 14. The method ofclaim 11, the receiving step further comprising: receiving solar energythrough a plurality of focusing/collimating elements; and combining thereceived solar energy through a plurality of light guides, opticalswitches, and optical splitters/combiners.
 15. The method of claim 11,wherein the directing step comprises directly providing the concentratedsolar energy into one of the heat chamber through one of: one or moreoptically transparent window shaped to reduce optical back reflectionand to seal working fluid in the heat chamber; and one or more lightguides extending into and terminating in the heat chamber, wherein theone or more light guides each comprise an angled tip shaped to reduceoptical back reflection.
 16. The method of claim 11, wherein thepredetermined time period comprise heating cycles for each of the one ormore piezoelectric generators; and wherein the heating cycles for eachof the one or more piezoelectric generators are offset from one another.17. A piezoelectric generator system, comprising: a solar energycollection mechanism; a plurality of heat chambers each coupled to thesolar energy collection mechanism to receive collected solar radiationand convert the collected solar radiation into heat; a plurality ofpiezoelectric element stacks each disposed to one of the heat chambersthrough a flexible bellow section; a switching element for the solarenergy collection mechanism, wherein the switching element is configuredto distribute solar energy collected by the solar energy collectionmechanism into the plurality of heat chambers in a pulsating manner. 18.The piezoelectric generator system of claim 17, further comprising: heatremoving elements disposed to each of the plurality of heat chambers.19. The piezoelectric generator system of claim 18, wherein the heatremoving elements comprise tubes with circulating water.
 20. Thepiezoelectric generator system of claim 18, wherein heating cycles foreach of the plurality of heat chambers are offset from one another.